Head gasket/cracked heads?

[77 K20]

Well after having the cam shaft, lifters, timing gear, ram horn manifolds installed, brand new exhaust and intake manifold replaced a few months ago the truck was running great. On one highway trip of 120 miles I lost a lot of oil from a leak- so found the oil pan gasket was leaking. Fixed that and replaced the PCV at the same time. Truck then ran great until....

yesterday. Drove 12 miles on the highway to do some grocery shopping. After shopping the truck was still fine, drove home. Started unloading the truck and then hear the truck puking coolant all over the ground. The truck was turned off- but overheated and then overfilled the overflow tank. (temperature was 67 degrees with light rain)

Figured if the truck was off and it overheated (while driving the temp gauge was at 1/4 like it always is) it must be the radiator cap. Took my car out and bought a new Stant one.

This morning I make sure the radiator is full. Install the new cap. Checked the engine oil. All is great. Drive on the highway 20 miles stop, turn off the truck. All is still great.

Then drove up the north fork road. It is a rough gravel road that ends at the canadian border. Made it all the way within 6 miles of the border and see a road closed sign. With the truck idling in drive I read the sign- about 40 seconds. I then looked at the temp gauge. It is now 1/2. I start driving and it cools down to 1/4. Had to make a 6 point turn to turn around. Truck heats up to 1/2. Start driving and cools to 1/4 again. Got behind one guy doing 20 mph and the truck started to get warm again. Passed him and got up to 40 mph. Truck cooled back down to 1/4. At this point I cranked the heater up and set the fan on high.

The mechanics shop was closer then my house so stopped by to talk to him (he left early for the holiday weekend). While the truck was sitting (turned off) it pukes more coolant out. Decide not to drive it and call the wife to pick me up. While I'm waiting for an hour I checked the truck over a bit. The oil that used to be full now barely registers on the dip stick. It looks normal- nice clean oil, but do not know where the estimated 2 quarts went. There are no oil leaks under the engine, or on the back of the tailgate. The radiator is about 1/2 way empty and the coolant reservoir is overfilled.

The drive today was only about 65 degrees. Not pulling anything. About 25 miles of it was pretty flat highway at 65 mph. Then the rest was dirt roads at 30-45 mph. Fairly flat also.

So quite pissed off right now. Work is not busy so I've been on job attached unemployment and will be for the next week and a half. I had a trip planed for the holiday weekend with this truck also.

Aaargg.... anyway guess I feel a little better after ranting. I'm in no mood to look at the truck as I'm likely to smash it into oblivion. Will be taking the car instead and go on a different trip. Will have time to look at it in about a week.

Not sure if it will be worth doing any more work on the engine or just save up and buy a new one. I just sunk $1100+ in it already and got bit in the ass.

 

[89Suburban]

You got smoke coming out of the tailpipe?


Posted from hell

 

[77 K20]

You got smoke coming out of the tailpipe?


Posted from hell

Nope- that is the odd thing. No blue smoke, no white smoke (steam).

And the truck ran smooth and perfect all day.

 

[chengny]

White smoke (water vapor) from the tail pipe?


For me that is the sure sign of a coolant to combustion space head gasket leak. If I don't see water (or vapor) issuing from the exhaust I don't immediately assume head gasket leak.

Pull the thermostat and see what happens. A sticking or failed t-stat will cause the same problems you describe. With the coolant flow from the heads to the radiator blocked off, pressurized steam pockets form. Eventually the pressure of these pockets overcome the water pump head pressure. When that happens, coolant is forced backwards through the pump and into the outlet tank of the radiator. The excess pressure in the radiator pops the cap and coolant gushes into the head tank/reservoir.

From there, it's a short trip to the pavement.

No coolant in the lube oil is another hopeful sign.

 

[89Suburban]

White smoke (water vapor) from the tail pipe?


For me that is the sure sign of a coolant to combustion space head gasket leak. If I don't see water (or vapor) issuing from the exhaust I don't immediately assume head gasket leak.

Pull the thermostat and see what happens. A sticking or failed t-stat will cause the same problems you describe. With the coolant flow from the heads to the radiator blocked off, pressurized steam pockets form. Eventually the pressure of these pockets overcome the water pump head pressure. When that happens, coolant is forced backwards through the pump and into the outlet tank of the radiator. The excess pressure in the radiator pops the cap and coolant gushes into the head tank/reservoir.

From there, it's a short trip to the pavement.

No coolant in the lube oil is another hopeful sign.

Can I get your opinion on drilled thermostats?


Posted From Hell

 

[77 K20]

Read as much as I could here and went out and bought a thermostat. The truck had been sitting for 5 hours. The overfull reservoir was still 100% full. Thought when the truck cooled off it should have sucked it back in?

Added a quart of oil, changed the thermostat and added a gallon of antifreeze/distilled water to the radiator. It was almost completely empty. Started the truck with the radiator cap off. Right away the heater hose return was pumping water into the radiator. After a few minutes the heater hoses were hot, but the upper radiator hose was cold. Reved the truck a few times to burp the system. Antifreeze level in the radiator dropped down and the upper hose started getting warm. Turned it off installed the radiator cap. Let idle for 10 minutes. Temp gauge at 1/4 (normal). Exhaust was clear- no smoke. Drove for about 10 miles. Stopped and idled for 10 minutes. Temp gauge was at 1/4 the whole time. But it is only about 50 degrees out (it is at night)


So I still don't trust it. It was fine yesterday for the first 45 miles of the drive. The day before it had issues after just 12 miles.

So other than sticking to well used roads (the areas I was wanting to travel with it is an hour or two from any town and is out of cell phone range) what else can I check?

Would doing a compression test be worth while at this point?

 

[chengny]

Failed head gaskets don't get better.

If you did have one (a bad H/G) you'd know it.

There would still be combustion gases in the coolant causing gas pockets that disrupt coolant flow.

Also, you'd have coolant getting into the cylinders and leaving with the exhaust - and cool ambient temperatures would not stop it.

Matter of fact, a coolant into combustion space leak is much easier to identify in cold weather. Any water that leaves the coolant system and gets into the exhaust gases is more easily condensed as it leaves the tail pipe. Still no vapor showing at the tail pipe right?

My money is on the t-stat replacement solving your problem.

But, if you really still feel there is a problem and want to diagnose - a leakdown test would provide a much more accurate picture of H/G integrity than a comp test.

For that matter, you could fabricate a rig to introduce compressed air into each cylinder. Take an old spark plug, knock the ceramic off and drill the guts out. Attach a hose to the metal part of the plug with a hose clamp and screw it in.

Do each cylinder one by one rotating the engine to bring both valves to the closed position.

Apply 80-100 psi to the combustion space through the spark plug hole. Leave it pressurised for 5 minutes or so. Remove the t-stat housing and stat and look down into the t-stat opening while the air is on.

A leaky head gasket will allow the compressed air to enter the coolant and you will know it right away. If you see bubbles in the coolant through the stat opening - your H/G is shot.

 

[89Suburban]

I am sure you could also rent a coolant system pressure tester as well to help diagnose. Did you drill a hole in the ring of the new thermostat?


Posted From Hell

 

[Green79Scottsdale]

Make sure the cooling system is topped off. Start the truck with the rad. cap off. If you get bubbles in the coolant, you have a bad head gasket.

I had this on our van last year. We loaded up to go to Grandpa and Grandma's house. As I backed out of the garage I thought there was more exhaust vapors than usual. But they soon went away. 3/4 of the way into the trip, on the highway, it let go. Combustion getting into the coolant passage. Towed it the rest of the way to G&G's, topped off the cooling system, start it, bubbles! Tear it down, sure enough, bad H/G.

As 89S said, might be a good thing to test the pressure to. My car was using coolant and having bouts of overheating. It was not leaking anywhere, and even the garage I took it to couldn't find the leak at first either. They finally pinpointed a very small leak at the lower intake manifold gasket (GM 3.1 V6). Tore into it and first thing I noticed is the bolts were literally finger tight! I probably could have just tightened them and been fine, but I had the new gaskets so I put them in.

Maybe go through and re-check the torque on your fasteners that were disturbed from the recent service you have been doing. Something may have loosened up and is now causing the grief. My car didn't show symptoms until 75k miles.

 

[77 K20]

This morning when I got up the overflow was still full. For some reason when the truck cooled off it didn't suck the coolant back into the engine. The hose from the radiator neck to the recovery tank is good (no cracks, holes). Oped the radiator cap and the fluid level was about 2" down. Sucked the antifreeze out of the overflow and added to the radiator until it was full. That left the overflow almost empty.
Went on a drive. Temp gauge did good- but got home and looked in the overflow reservoir. It was 80% full with white foam on top (appears the foam was only about a half inch on the top).

So need to either burp the system more or still a head gasket type issue. But I'm leaving for a trip now so it will have to wait until I get back to check it out more.

I didn't drill a hole in the new thermostat. Still no sign of any vapor out the exhaust.

 

[89Suburban]

Yikes. Try taking a look at the plugs and read them for clues too.


Posted from hell

 

[77 K20]

Yikes. Try taking a look at the plugs and read them for clues too.


Posted from hell

Instead of packing and leaving on my trip I keep reading about head gasket stuff online. (but the wife is starting to get annoyed)

Just found out that NAPA supposedly has some sort of test strip that you dip into the anti freeze and it will tell you if there are exhaust gasses that have been bubbling thru the coolant. Didn't know that. Supposedly Napa Balkamp # BK 7001006

I'll be picking up some of that to see what it says.

 

[chengny]

For some reason when the truck cooled off it didn't suck the coolant back into the engine. The hose from the radiator neck to the recovery tank is good (no cracks, holes). Oped the radiator cap and the fluid level was about 2" down.

That's perfectly normal - especially with all the opening & closing you have been doing.

You need to fill the sytem to the normal levels:

1. The radiator only to the point where the top row of tubes is covered.

2. The expansion tank to the mid-level and mark it with a Sharpie.

Check all hose clamps for tightness.

Then close it up, walk away and drive the truck normally.

Don't open the system for awhile - resist the temptation to even open the radiator cap .

Just monitor the temp gauge while driving and (after a few days) note any change in the coolant reservoir level. Re-fill the tank to the Sharpie mark and note the amount of coolant added.

After a week or so, you'll get an idea of the rate that coolant is being lost (if any).

 

[77 K20]

A slight update: I got a set of cast iron heads from my dad's 290hp 350. They only have 20,000 miles on them. Don't know if these heads are much different than the ones on my '77. Hard to find info on my stock heads.
The new ones are 1.94 intake and 1.50 exhaust. Part number 93438648.

I ordered some fel-pro perma torque head gaskets that are supposed to be pretty good. The odd thing is they only had 3 steam holes (instead of 6). Took them to a machine shop and had the 3 holes drilled. The machine shop didn't seem to be concerned. They said as long as there is a path out for the steam 3 holes are as good as 6, and now there is less chance of future head gasket problems.

The truck should be back together by next week. Hopefully all goes ok.

 

[Jims86]

A slight update: I got a set of cast iron heads from my dad's 290hp 350. They only have 20,000 miles on them. Don't know if these heads are much different than the ones on my '77. Hard to find info on my stock heads.
The new ones are 1.94 intake and 1.50 exhaust. Part number 93438648.

I ordered some fel-pro perma torque head gaskets that are supposed to be pretty good. The odd thing is they only had 3 steam holes (instead of 6). Took them to a machine shop and had the 3 holes drilled. The machine shop didn't seem to be concerned. They said as long as there is a path out for the steam 3 holes are as good as 6, and now there is less chance of future head gasket problems.

The truck should be back together by next week. Hopefully all goes ok.

They are smogger heads that were used on all of the 350's up to 86, but the ones from the crate/replacement engines wer treated to the larger 1.95 intake and 1.6 exhaust valves. Decent heads If your truck is just a truck, and not a hotrod.